While Tomoyo provides costumes for Sakura to wear when capturing Clow Cards (and other magical excursions), Sakura’s first capture takes place before Tomoyo knows about Sakura’s Cardcaptor position. Instead, Sakura sets out at night in her pajamas, wearing her rollerblades and protective gear, making for a strange outfit to wear while capturing a Clow Card.
Sakura wears this outfit in the first episode, “Sakura and the Mysterious Magic Book”, although she may wear the same pajamas in later episodes. (Perhaps I should investigate, and list all matching episodes?)
Sakura’s pink pajamas feature a “night sky” theme. With a crecent moon and a star on the collar, and star over the buttons down the front, this outfit is fitting of her position much later in the series. To keep from being too pink, the collar and cuffs of the outfit are an off-white color. Sakura also wears her hair up with pink beaded hair accessories, color coordinated with her pajamas.
Against wind, a loose-fitting outfit such as pajamas doesn’t seem the be the most appropriate thing to wear. Luckily for this Cardcaptor, she has a best friend able to design and choose more appropriate outfits for future magical confrontations.
The rollarblades were obviously chosen to wear because Sakura can travel more quickly with them, and it’s a form of transportation she’s used to. If Japanese pajamas are anything like those in the USA, the fabric’s probably not as strong as day clothes, so the protective gear is especially required for her elbows and knees. That, and she’s going against a giant wind bird undoubtedly capable of blowing her halfway across town.